This is an unusual situation where I have an NFS server currently serving out MULTIPLE clients over several variants of Linux and UNIX successfully (world permissions) except for a SINGLE client. Even the other Linux (SuSE) clients are mounting successfully with defaults without incident.

THIS client 'just stopped working' and the only error from the /var/log/messages file indicates that it could not contact the NFS server: operation timed out.

It all gets fixed if I use 'tcp' as the mount option, bypassing UDP altogether. However this client had been working up until this week and AFAIK no changes were made to this client. Again, other Linux clients IN THE SAME ROOM and ON THE SAME SWITCH are doing just fine and not having this problem!

Even the client system itself mounts two other NFS file systems from a different server without this workaround (IRIX server, believe it or not) but cannot mount the SuSE server without using the 'tcp' flag.

Any clues here? I've googled this particular issue in bug reports but to no avail. Here's the output from the client side of what's being served:

rpcinfo -p hardhead
program vers proto port
100000 2 tcp 111 portmapper
100000 2 udp 111 portmapper
390436 1 tcp 9907
390435 1 tcp 9890
390113 1 tcp 7937
390115 1 tcp 8494
100024 1 udp 32771 status
100021 1 udp 32771 nlockmgr
100021 3 udp 32771 nlockmgr
100021 4 udp 32771 nlockmgr
100024 1 tcp 42410 status
100021 1 tcp 42410 nlockmgr
100021 3 tcp 42410 nlockmgr
100021 4 tcp 42410 nlockmgr
390103 2 tcp 9801
390109 2 tcp 9801
390110 1 tcp 9801
390120 1 tcp 9801
390109 2 udp 9715
391060 1 tcp 850
390107 5 tcp 9289
390107 6 tcp 9289
390402 1 tcp 9011
390105 5 tcp 9164
390105 6 tcp 9164
390433 1 tcp 9598
100003 2 udp 2049 nfs
100003 3 udp 2049 nfs
100003 2 tcp 2049 nfs
100003 3 tcp 2049 nfs
100005 1 udp 805 mountd
100005 1 tcp 806 mountd
100005 2 udp 805 mountd
100005 2 tcp 806 mountd
100005 3 udp 805 mountd
100005 3 tcp 806 mountd
391029 1 tcp 46557
391030 1 tcp 54937
390104 105 tcp 9420
390430 1 tcp 8334
390429 101 tcp 9183

As you can see, NFS is available on both udp and tcp versions 2 and 3.